Centrifugal compressors are used to compress a fluid, such as air, and are a part of turbomachines, turbochargers, water pumps, and other applications where compressing a fluid is useful. Centrifugal compressors include an impeller and a shroud that encloses the impeller. Fluid enters the centrifugal compressor at an inlet and is expelled at an outlet. The impeller, which includes a plurality of blades extending from a hub, rotates to accelerate the fluid. The pressure associated with the fluid increases as the fluid is accelerated by the blades and as the fluid contacts the shroud. Thus, low pressure fluid that enters the inlet of the centrifugal compressor is converted to high pressure fluid at the outlet because of the rotational energy of the impeller.
One problem with currently available centrifugal compressors is that fluid within the centrifugal compressor is typically not efficiently compressed by the impeller. There is a gap between the outermost extent of the impeller blades and the shroud, and the fluid in this gap is not efficiently compressed by the impeller blades. Also, fluid proximal the hub of the impeller is not efficiently compressed by the impeller blades. These inefficiencies arise from the fact that fluid in the gap and fluid proximal the hub may churn or shear instead of compressing efficiently. This lack of efficiency in compressing fluid results in decreased performance and higher fuel costs.